Macrolides are multi-membered lactone rings having one or more deoxy sugars as substituents. Erythromycin, azithromycin, and clarithromycin are macrolides that have bacteriostatic and/or bactericidal activity.
Tacrolimus (FK 506) is also a macrolide antibiotic that is also an immunosuppressive agent. More potent than cyclosporin, tacrolimus has a selective inhibitory effect on T-lymphocytes.
Ascomycin is an immunomodulating macrolactam that reportedly blocks T-cell activation, inhibits cytokine release, and inhibits mast cell activation. “The mechanism of action of ascomycin is very similar to that of cyclosporin and of tacrolimus, although the three compounds have different chemical structures.” C. E. Griffiths, Ascomycin: An Advance in the Management of Atopic Dermatitis. 144 Br. J. Dermatol., No. 4,679,679 (April 2001).
Pimecrolimus is a macrolactam ascomycin derivative that reportedly inhibits production of pro-inflammatory cytokines by T cells and mast cells. The Merck Index 1331 (Maryadele J. O'Neil et al. eds., 13th ed. 2001). Pimecrolimus is used as an immunosuppressant. Id.
Sirolimus, another macrolide, is also an immunosuppressant. Sirolimus has been administered with cyclosporin and corticosteroids after transplantation to avoid graft rejection. Martindale: The Complete Drug Reference 568 (Sean C. Sweetman ed., Pharmaceutical Press 33rd ed. 2002).
Everolimus, a derivative of sirolimus, is an immunosuppressant used in organ transplantation. Martindale at 539.
The macrolides are typically obtained by fermentation, although synthetic routes to some are known. The present extraction method offers several advantages over the prior art. For example, the entire fermentation broth can be used as starting material for the present method (“whole broth method”) and the use of hydrophobic extraction solvent results in an efficient extraction yield, leaving behind most water-soluble impurities, with removal of mycelium in one step. Concentration under reduced pressure at temperature above 25° C. and reduced pressure results in a high evaporation rate of solvent without precipitation or decomposition of the macrolide. Further advantages of the present invention will be apparent to the skilled artisan.